This invention relates to a magneto-resistance effect magnetic head which may be employed for reading out information recorded on a magnetic recording medium, such as a hard disc.
Recently, developments in a magneto-resistance effect magnetic head (MR head) employing a magneto-resistance effect element (MR element) exhibiting the magneto-resistance effect, such as permalloy, are proceeding vigorously.
The MR head is designed to read out information recorded on the magnetic recording medium by detecting changes in resistance of the MR element by a signal magnetic field leaked out of the magnetic recording medium.
Such a magnetic head, which is superior to typical magnetic induction magnetic head in short wavelength sensitivity, is thought to afford high sensitivity in narrow track reproduction, short wavelength reproduction in ultra-low speed reproduction.
The MR head has an MR element 103, sandwiched between a pair of shielding magnetic members 101, 102, and a bias conductor 104 arranged on the MR element 103 for applying the bias magnetic field thereto, as shown in FIG. 1. The bias magnetic field, induced by the bias current supplied to the bias conductor 104, is applied to the MR element 103 towards the rear side from a surface 105 adapted to have sliding contact with the magnetic recording medium.
If the bias conductor 104 is provided directly above the MR device 103, the following inconveniences arise. First, waveform distortion is produced in the lone waveform A indicative of changes in the magnetic flux acting on respective positions of the MR device 103, as shown in FIG. 2. If there is any waveform distortion, linear recording density cannot be increased, such that the recording capacity of the recording medium cannot be increased. Among the causes of such waveform distortion is the non-uniformity in the distribution of the bias magnetic field.
Such non-uniformity in the distribution of the bias magnetic field is produced by the bias magnetic flux entering the MR device 103 and leaking to an underlying layer of the shielding magnetic member 101. Should there be such non-uniformity in the distribution of the bias magnetic field, the region of the MR device having high bias magnetic field strength is magnetically saturated in a short time, such that the signal magnetic flux cannot enter such region. On the other hand, should there be any variation in the intensity of the bias magnetic field, the operating point tends to be shifted to the non-linear region of the MR sensitivity characteristics, thus producing distortion in the playback waveform.
Second, if the shield magnetic member 101 is present directly below the MR device 103, the magnetic wall is shifted due to disturbance in the core magnetic domain, thus producing Barkhausen noise.